Tools comprising, as abrasive, particles of superabrasive such as diamond and cubic boron nitride, are produced and employed widely for cutting and drilling in various forms, such as circular and annular cutting saws and blades, band saws, gang saws and core drills. They can be categorized into powder metallurgical and electrodeposited tools by the technique applied for fixing the abrasive to the corresponding base member, or stay, of metal.
The former group, which are used principally for cutting or drilling stones, concrete blocks, and common ceramics, are produced either with a continuous peripheral edge or, more commonly, with segmented edges such that arc-shaped or rectangular chips of powder metallurgical composite of metal and diamond are brazed to a circular base plate intermittently around the periphery. Gang saws and like linear tools, with such diamond chips brazed along appropriate straight base bodies, are also used in some specific applications. However since the chips are usually brazed to the base plate mainly on the peripheral surface, which is an area only as wide as the plate thickness, there are some cases reported of abrupt chip removal due to the insufficient retention during the cutting process. So metallurgical chip tools usually rely upon a rather thick base member of steel to provide an adequate retention for the chips. Further, due to difficulty in the arrangement in alignment of the chips when brazed to the base plate, the kerf becomes even larger and thus the stock to be removed in the cutting is substantial, disadvantageously.
On the other hand, electrodeposited tools are manufactured by spreading superabrasive particles over the edge-forming section and an adjacent base plate area, and depositing metal by electrolysis to fix said particles. The process is conducted for the both sides of the base plate. Such blades can minimize the kerf loss and are often employed in applications which do not tolerate a substantial cutting loss, as in the slicing into wafers of silicon or other expensive semi-conducting material, for example. For this purpose it is desired that the overall thickness of the blade, with the edges combined, be minimized, and the number of stacked layers of abrasive particles is limited to two to three, or one. Since such small number of layers are deposited in the formation of cutting edges on the peripheral surface, which is in parallel with plate thickness, and further smaller particle sizes are favored due to the decreased kerf width and free-cut performance, the resulting tool life remains at a low level. For, in such tools, the cutting process is apparently achieved mainly with particles which are present in the cylindrical surface or on the sides of the base member in adjacency, the rest serving to a finishing work by smoothing the as-cut work surface. As the particles are worn out to expose the plate, a substantial increase in cutting load results to end the life of cutting tool.
So, while achieving a good performance in free-cut efficiency, electrodeposited tools do not necessarily exhibit a sufficient life usually with a limited number of abrasive particle layers available and effective for the cutting process. The kerf width could, and should, be less, even if they may be smaller commonly than with the above said powder metallurgic type. Some tool designs have been published which are free of such problems.
JP, U, 62-144117, for example, describes a technique of manufacturing a thin blade saw by a repeated electrodeposition of abrasive particle layers along the periphery of the base plate, while suppressing deposition on either side. While the kerf apparently can be minimized somehow by limiting the abrasive layer width close to the base member thickness, it is actually very difficult to form a stack of several layers within the given range of thickness by repeated electrodeposition processes. As a result the tool life remains rather short, with the number of stacked layers limited to two or so at maximum, in the view of the achievable form precision.
Other published techniques include the reduction of edge thickness by grinding the base member at the edge forming sites, on the both sides, before the layer of abrasive particles is deposited (as described in JP, U, 58-84849), or by depositing particles to fill a series of alternating recesses provided on the sides of a linear base member along the periphery (JP, U, 63-127878). While those techniques may be effective for decreasing somewhat the material loss by the cutting, the tools cannot show any increase in life, which ends up when the base member becomes exposed after the surface particles are substantially worn out and popped out.
Thus one of the principal objects of the invention is to provide a superabrasive deposited cutting edge and a method of manufacturing the same, which has effectively eliminated of the above described drawbacks and permits, as generally desired, a substantial improvement in tool life, while securing the inherent free-cut performance and minimal cutting width.
In the description the term "free-cut" is used to refer to a physical parameter, instead of customary usage in a somewhat subjective sense, and defined as an index of "stock removal relative to the load applied".